1. Field of the Invention
The present invention relates to a color control method, and more particularly, to a color control method for LED lighting systems.
2. Description of the Prior Art
Due to lightweight, small size, low power consumption and high-bright lighting capability, light emitting diodes (LEDs) are now in widespread use, including a variety of indication applications, indoor or outdoor lighting applications, vehicle auxiliary lighting applications, camera flashlights, and so forth. In particular, the designs of backlights for different display panels are switched from traditional cold cathode fluorescent lamps (CCFLs) or external electrode fluorescent lamps (EEFLs) to LED lighting modules gradually. While the LED lighting modules are applied to devise the backlights for different display panels, corresponding control methods for the LED lighting modules are required to control the luminance and chromaticity of light outputs for achieving high-quality visual appearances.
FIG. 1 is a functional block diagram schematically showing a prior-art LED lighting system 100. The LED lighting system 100 comprises an LED module 101, an LED driving circuit 111, a color sensor 180, and a controller 150. The LED driving circuit 111 is utilized to provide a driving signal to the LED module 101. The color sensor 180 detects the light emitted from the LED module 101 for generating a feedback signal. The controller 150 generates a control signal based on the feedback signal. Then, the LED driving circuit 111 is capable of regulating the driving signal based on the control signal so that the LED module 101 is able to generate the light having desired luminance and chromaticity.
However, when the operating temperature of the LED dice of the LED module 101 is rising, wavelength shifts will occur to the light emitted from the LED module 101 accordingly. The prior-art LED lighting system 100 is not able to compensate the wavelength shifts in response to temperature variations. That is, the control accuracy concerning the luminance and chromaticity of the light generate by the LED module 101 is getting worse as the operating temperature of the LED dice of the LED module 101 rises.